1. Field of the Invention
This invention relates to a tape driving system for a magnetic transfer apparatus in which at least two magnetic tapes are pressed against the outer periphery of a rotary drum and driven thereon in close pressure contact with one another. More particularly, it relates to a tape drive device useful in a magnetic transfer apparatus in which magnetic recording on a master tape is transferred to a slave tape in intimate contact with said master tape while said master and slave tapes are driven in this state on the periphery of the rotary drum.
2. Description of the Prior Art
In recent years, magnetic recording and reproducing apparatus such as video tape recorder or audio tape recorder have become very popular. In keeping pace therewith, there is an increasing demand for various prerecorded tapes. Thus it has become necessary to duplicate a large number of copy tapes from a prerecorded master tape (also called mother tape).
As means for preparing these copy tapes, it is known to reproduce magnetic recording on the master tape and to rerecord the output signal on an unrecorded tape or slave tape (so-called dubbing method) or to magnetically transfer the residual magnetic pattern on the master tape to the unrecorded or slave tape (magnetic transfer method). In the conventional practice, the first method (dubbing method) is predominant and the signals from a master reproducing device or tape deck are sent to plural copy tape recorders or tape decks for rerecording.
However, when resorting to dubbing, at least two tape decks, that is, a master tape reproducing device and a copy tape recording device are required, resulting in elevated equipment costs. In addition, signal deterioration may be caused through the signal reproducing and recording process. Above all, since the recording tracks are formed diagonally across the tape width in video tape recorders, the recording track pattern obtained with the copying tape decks may vary on account of manufacturing tolerances of the rotary heads of the copying tape decks. The result is poor interchangeability, that is, variable image quality obtained with different reproducing tape decks.
Although not so popular in the past as the first method because of, for instance, lowered transfer signal intensity, the second method, that is, the magnetic transfer method, has come to the stage of commercial application with development of the master tape with high residual magnetism and progress in magnetic transfer technology. With the magnetic transfer method, copy tapes can be prepared by a unitary device and the playback and recording process can be eliminated. In this manner, the playback or recording heads such as rotary magnetic heads, playback circuits or recording circuits can be dispensed with, thus resulting in a simplified structure and elimination of signal deterioration caused by signal playback and recording. In addition, even when the recording tracks are formed diagonally across the tape width, as in the case of the video tape recorder, since the master and copy tapes are intimately contacted with each other, and the magnetic pattern is directly transferred from the master tape to the copy tape, the recording track pattern on the copy tape may be substantially identical in signal quality or accuracy with that on the master tape. In this manner, the copy tapes obtained with the second method may be completely free from fluctuations and superior in interchangeability.
The magnetic transfer apparatus for producing copy tapes through magnetic transfer is provided with a tape driving system adapted for simultaneously driving at least two magnetic tapes, that is, a master or mother tape and a slave or copy tape, that are wound on the outer periphery of a rotary or transfer drum in intimate contact with one another. When it is desired to suddenly stop the travel of these two or more tapes while being driven simultaneously, since the tape supply and take-up reels have different rotational inertia, it is not possible to stop the rotation of the reels simultaneously, thus resulting in unusual tension applied to the respective tapes. Such unusual tension may be prevented in some measure by applying a brake slowly to the respective tape reels. However, this is not desirable because effective magnetic transfer is inhibited during the braking period thus lowering the operating efficiency of the magnetic transfer apparatus. For instance, even when a single prerecorded program can be transferred in several tens of seconds on account of high speed transfer technology, the overall transfer efficiency would be lowered if nearly several tens of seconds are required in stopping the tape travel.